The present invention relates to a quick action band saw blade tensioning device for quickly adjusting the tension force applied to the band saw blade and for maintaining the tensioning force in place following adjustment.
Band saw machines include a supporting frame having upper and lower band saw supporting wheels (two wheel band saw) or upper and lower band saw supporting wheels and a driven wheel (three wheel band saw), all of which are rotatably mounted to the supporting frame. A band saw is entrained about the upper and lower band saw supporting wheels in the two band saw wheel machine and about the upper and lower supporting wheels and a driven wheel in the three wheel band saw machine. For driving the band saw in an endless closed loop path about the band saw wheel supports, an electric motor is operatively connected to one of the upper and lower band saw supporting wheels in the two wheel band saw machine or to the driven wheel in the three wheel band saw machine to drive the band saw in its endless closed loop path for cutting workpieces, as is well known.
The tensioning force applied to a band saw blade must be adjusted from time to time, in order to operate the band saw blade with maximum efficiency and cutting capability. Under normal procedures, band saw blade tensioning is controlled through the use of a rotating knob and coil spring adjustment mechanism such as disclosed, for example, in U.S. Pat. Nos. 2,644,491 and 2,744,547. As disclosed in both of these patents, the rotating knob and coil spring tensioning force adjusting mechanism operates to move one of the upper and lower supporting wheels toward and away from one another for adjustment of the band saw blade tension. Another device shown in U.S. Pat. No. 2,711,196 includes a slide member which is adjusted upwardly or downwardly to continuously apply tension to a band saw blade.
Although such known devices have been effective in providing the desired tensioning force to a band saw blade, they have several known deficiencies. In the rotating knob with compression spring type of device, it is necessary to rotate the knob several times, and in some cases, many times, in order to obtain the desired adjustment. As will be understood, this can be a time consuming procedure. Also, instructions for band saw machines suggest that it is desirable to relieve the band saw blade tension following use so as to remove the load on the supporting components, which can lead to other problems in the band saw. In either the rotating knob/compression spring tensioning force devices and in other continuous tension force mechanisms, substantial time is also required to relieve the tension force on the band saw blade and then re-engage the tensioning force at a later time for subsequent use. As will be appreciated in the disclosure of this invention in the discussion that follows, the aforementioned and other problems have been overcome in the quick action band saw blade tensioning device of the present invention.